Communications by mobile phones use radio waves. Thus, even within a communication coverage area, in a radio shadow area where radio waves from an outdoor base station (hereinafter, referred to as a “macrocell base station”) are difficult to reach (or do not reach), communications by mobile phones cannot be performed. Hence, in order to enable communications by mobile phones even in the radio shadow area, the construction of a communication system using a compact base station is considered.
In this communication system, a compact base station (hereinafter, referred to as a “femtocell base station”) having, as its coverage area, a very small cell (femtocell) with a radius of the order of several meters to several tens of meters is installed in a radio shadow area. In addition, the femtocell base station is connected to a mobile communication network of a mobile service provider through a wire communication line. Therefore, mobile phones in the radio shadow area are connected to the mobile communication network through the femtocell base station and the wire communication line. As a result, even in the radio shadow area, communications by mobile phones are enabled.
Note that Japanese Unexamined Patent Publication No. 2004-15103 (Patent Literature 1) discloses a communication system including a radio base station installed in an optical communication subscriber's home. In this communication system, a signal from a mobile phone used in the subscriber's home is transmitted from the radio base station in the home to a local office through an optical communication cable and is then transmitted from the local office to various networks such as an IP network, a general telephone switching network, and a mobile communication switching network.